Mars Global Surveyor
Mars Orbiter Camera

Nirgal Vallis and its Windblown Dunes

Nirgal Vallis is a narrow valley system that stretches
approximately 420 kilometers (260 miles) across the martian
surface near 28°S latitude, north of the large basin,
Argyre. The floor of the valley system is largely covered
with light-toned dunes and ripples. These windblown features
obscure most of the original morphology of the valley floor.
This view of a small portion of Nirgal Vallis was obtained
by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC)
during Extended Mission subphase E02 on March 29, 2001. In
each short tributary valley, dunes have a somewhat different
orientation compared to those in the other valleys. The dune
patterns here indicate that winds are locally controlled by
the shape and orientation of each valley. The dunes just
left of the center of the image have small craters on them,
formed by meteor impact. The craters indicate that the dunes
are not fresh, modern features, but are considerably older
than they might at first seem. This image covers an area
3 km (1.9 mi) wide and is illuminated from the upper left.

Image Credit: NASA/JPL/Malin Space Science Systems

Malin Space Science Systems and the California Institute of
Technology built the MOC using spare hardware from the Mars Observer
mission. MSSS operates the camera from its facilities in San Diego,
CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project
operates the Mars Global Surveyor spacecraft with its industrial
partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA
and Denver, CO.